/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package io.netty.handler.codec.http2;

import io.netty.channel.Channel;
import io.netty.channel.ChannelDuplexHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.embedded.EmbeddedChannel;
import io.netty.util.ReferenceCountUtil;
import io.netty.util.internal.PlatformDependent;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.locks.LockSupport;

import static java.util.concurrent.TimeUnit.MILLISECONDS;

/**
 * Channel handler that allows to easily access inbound messages.
 */
public class LastInboundHandler extends ChannelDuplexHandler
{
    private final List<Object> queue = new ArrayList<Object>();

    private Throwable lastException;

    private ChannelHandlerContext ctx;

    private boolean channelActive;

    @Override
    public void handlerAdded(ChannelHandlerContext ctx)
    {
        this.ctx = ctx;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception
    {
        if (channelActive)
        {
            throw new IllegalStateException(
                    "channelActive may only be fired once.");
        }
        channelActive = true;
        super.channelActive(ctx);
    }

    public boolean isChannelActive()
    {
        return channelActive;
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception
    {
        if (!channelActive)
        {
            throw new IllegalStateException(
                    "channelInactive may only be fired once after channelActive.");
        }
        channelActive = false;
        super.channelInactive(ctx);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception
    {
        queue.add(msg);
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt)
            throws Exception
    {
        queue.add(new UserEvent(evt));
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception
    {
        if (lastException != null)
        {
            cause.printStackTrace();
        }
        else
        {
            lastException = cause;
        }
    }

    public void checkException() throws Exception
    {
        if (lastException == null)
        {
            return;
        }
        Throwable t = lastException;
        lastException = null;
        PlatformDependent.throwException(t);
    }

    @SuppressWarnings("unchecked")
    public <T> T readInbound()
    {
        for (int i = 0; i < queue.size(); i++)
        {
            Object o = queue.get(i);
            if (!(o instanceof UserEvent))
            {
                queue.remove(i);
                return (T) o;
            }
        }

        return null;
    }

    public <T> T blockingReadInbound()
    {
        T msg;
        while ((msg = readInbound()) == null)
        {
            LockSupport.parkNanos(MILLISECONDS.toNanos(10));
        }
        return msg;
    }

    @SuppressWarnings("unchecked")
    public <T> T readUserEvent()
    {
        for (int i = 0; i < queue.size(); i++)
        {
            Object o = queue.get(i);
            if (o instanceof UserEvent)
            {
                queue.remove(i);
                return (T) ((UserEvent) o).evt;
            }
        }

        return null;
    }

    /**
     * Useful to test order of events and messages.
     */
    @SuppressWarnings("unchecked")
    public <T> T readInboundMessageOrUserEvent()
    {
        if (queue.isEmpty())
        {
            return null;
        }
        Object o = queue.remove(0);
        if (o instanceof UserEvent)
        {
            return (T) ((UserEvent) o).evt;
        }
        return (T) o;
    }

    public void writeOutbound(Object... msgs) throws Exception
    {
        for (Object msg : msgs)
        {
            ctx.write(msg);
        }
        ctx.flush();
        EmbeddedChannel ch = (EmbeddedChannel) ctx.channel();
        ch.runPendingTasks();
        ch.checkException();
        checkException();
    }

    public void finishAndReleaseAll() throws Exception
    {
        checkException();
        Object o;
        while ((o = readInboundMessageOrUserEvent()) != null)
        {
            ReferenceCountUtil.release(o);
        }
    }

    public Channel channel()
    {
        return ctx.channel();
    }

    private static final class UserEvent
    {
        private final Object evt;

        UserEvent(Object evt)
        {
            this.evt = evt;
        }
    }
}
